Method of manufacturing a semiconductor device having a multi-layered wiring structure

ABSTRACT

An insulating portion of the respective wiring layers for a semiconductor device is constituted of insulating films. The one insulating film is made of a material whose conductivity is higher than that of the other insulating film that is made of an ordinary silicon oxide film and is provided in contact with the wiring. An electric charge accumulated in the wiring generated in the course of manufacture of the semiconductor device is discharged through the one insulating film at a stage where a charge accumulation in the wiring is low. This permits the heat release value generated through the discharge can be suppressed to a low level, and the short-circuiting failure between adjacent wirings can be suppressed or prevented.

BACKGROUND OF THE INVENTION

This invention relates to a method of manufacturing a semiconductor device. More particularly, the invention relates to an effective technique for the formation of wiring in the manufacture of semiconductor devices.

The wiring structure of a semiconductor device includes wirings for passing signals or an electric current, and an insulating film is provided for insulating the wirings. It has been accepted that the wirings of a semiconductor device are provided for the purpose of lowering the resistance, and the insulating film is provided for the purpose of achieving complete insulation.

The wiring structure of a semiconductor device is described, for example, in Japanese Patent Application Laid-open No. Hei 8 (1996)-204006, which discloses a technique for covering a wiring with an etch stopper film and a technique for arranging a wiring on an etch stopper film.

[Patent Document]

Japanese Patent Application Laid-open No. Hei 8 (1996)-204006.

SUMMARY OF THE INVENTION

In this connection, we have found for the first time that the above-mentioned wiring techniques have the following problems.

When an electric charge built up in a wiring in the course of the process of manufacture of a semiconductor device exceeds a given level, a discharge takes place between adjacent wirings. As a result, high heat energy is instantaneously generated between adjacent wirings to deform the material of the wiring, with the attendant problem that short-circuiting takes place between adjacent wirings. Especially, this problem is apt to occur in a case where, as at least one objective wiring, there is a long wiring that is likely to build up an electric charge therein, or this problem can occur at a portion where wirings having a potential difference are arranged adjacent to each other. Moreover, as wirings become more highly integrated, the space between adjacent wirings becomes narrow, thereby causing the problem to become more pronounced.

An object of the present invention is to provide a technique for suppressing or preventing a failure due to short-circuiting between wirings of a semiconductor device.

The above and other objects and novel features of the present invention will become apparent from the description provided in this specification and from the accompanying drawings.

Among those features set out in the present application, a typical feature of the present invention can be briefly summarized as follows. The invention is contemplated to provide a wiring structure for a semiconductor device wherein an insulating film used therein has the function of permitting an electric charge that has accumulated in the wiring to escape.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing, in the course of a manufacturing process, a typical portion of a semiconductor device, illustrating a conventional problem found by us for the first time;

FIG. 2 is a sectional view showing an example of a typical portion of a semiconductor device according to one embodiment of the invention;

FIG. 3 is an enlarged, sectional view of region A of FIG. 2;

FIG. 4 is a graph showing the relation between current I and voltage V of an ordinary silicon oxide film;

FIG. 5 is a graph showing the relation between current I and voltage V of a silicon-rich silicon oxide film;

FIG. 6 is a graph showing the relation between current I and voltage V of a silicon-rich silicon oxide film;

FIG. 7 is a graph showing the relation between current I and voltage V of a silicon-rich silicon oxide film;

FIG. 8 is a graph showing the relation for comparison between the refractive index and the current of a silicon oxide film having a thickness of approximately 30 nm;

FIG. 9 is a graph showing the relation between the thickness and the current of a silicon-rich silicon oxide film having a refractive index of 1.55;

FIG. 10 is a graph showing the relation between current I and voltage V of a silicon oxynitride film;

FIG. 11 is a diagram showing an example of a cleaning device used in the manufacturing process of a semiconductor device according to the embodiment of the invention;

FIG. 12 is a sectional view of a typical portion of a wafer in the course of the process of manufacture of the semiconductor device of FIGS. 2 and 3;

FIG. 13 is a sectional view of a typical portion in the course of manufacture of the semiconductor device subsequent to FIG. 12;

FIG. 14 is a sectional view of a typical portion in the course of manufacture of the semiconductor device subsequent to FIG. 13;

FIG. 15 is a sectional view of a typical portion in the course of manufacture of the semiconductor device subsequent to FIG. 14;

FIG. 16 is a sectional view of a typical portion in the course of the manufacture of the semiconductor device subsequent to FIG. 15;

FIG. 17 is a timing chart showing a film-forming sequence in the formation of an insulating film of the semiconductor device of FIGS. 2 and 3;

FIG. 18 is a sectional view of a typical portion of a semiconductor device according to another embodiment of the invention;

FIG. 19 is a sectional view of a typical portion of a wafer in the course of manufacture of the semiconductor device of FIG. 18;

FIG. 20 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 19;

FIG. 21 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 20;

FIG. 22 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 21;

FIG. 23 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 22;

FIG. 24 is a diagrammatic plan view of a typical portion of a semiconductor device according to a further embodiment of the invention;

FIG. 25 is a sectional view, taken along the line X1—X1 in FIG. 24;

FIG. 26 is a sectional view of a structure illustrating the defect which we have studied;

FIG. 27 is a sectional view of a typical portion of a semiconductor device according to a still further embodiment of the invention;

FIG. 28 is a sectional view of a typical portion in the course of manufacture of a semiconductor device for illustrating the problem checked by us;

FIG. 29 is a sectional view of a typical portion of a wafer in the course of manufacture of the semiconductor device subsequent to FIG. 28;

FIG. 30 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 29;

FIG. 31 is a sectional view of a typical portion of a semiconductor device according to another embodiment of the invention;

FIG. 32 is a sectional view of a typical portion of a semiconductor device according to still another embodiment of the invention;

FIG. 33 is a sectional view of a typical portion in the course of manufacture of a semiconductor device for illustrating the problem checked by us;

FIG. 34 is a sectional view of a typical portion of a semiconductor device according to yet another embodiment of the invention;

FIG. 35 is a sectional view of a typical portion of a semiconductor device according to a further embodiment of the invention;

FIG. 36 is a sectional view of a typical portion of a semiconductor device according to another embodiment of the invention;

FIG. 37 is a sectional view of a typical portion showing the state where contact holes and plugs are provided at the semiconductor device of FIG. 36;

FIG. 38 is a sectional view of a typical portion of a semiconductor device according to another embodiment of the invention;

FIG. 39 is a sectional view of a typical portion at a face vertical to the section of FIG. 38;

FIG. 40 is a sectional view of a typical portion of a semiconductor device according to another embodiment of the invention;

FIG. 41 is a sectional view of a typical portion of a semiconductor device according to still another embodiment of the invention;

FIG. 42 is an enlarged sectional view of the region G of FIG. 40;

FIG. 43 is a sectional view of a typical portion of a wafer in the course of manufacture of the semiconductor device of FIG. 41;

FIG. 44 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 43;

FIG. 45 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 44;

FIG. 46 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 45;

FIG. 47 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 46;

FIG. 48 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 47;

FIG. 49 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 48;

FIG. 50 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 49;

FIG. 51 is a sectional view of a typical portion of a semiconductor device according to another embodiment of the invention;

FIG. 52 is a sectional view of a typical portion of a wafer in the course of manufacture of the semiconductor device of FIG. 51;

FIG. 53 is a sectional view of a typical portion of the wafer in the source of manufacture of the semiconductor device subsequent to FIG. 52;

FIG. 54 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 53;

FIG. 55 is a sectional view of a typical portion of the wafer in the course of manufacture of the semiconductor device subsequent to FIG. 54;

FIG. 56 is a plan view of a semiconductor chip of a semiconductor device according to another embodiment of the invention;

FIG. 57 is an enlarged plan view of the region J of FIG. 56;

FIG. 58 is a sectional view taken along line X2—X2 in FIG. 57;

FIG. 59 is a sectional view taken along line Y1—Y1 in FIG. 57;

FIG. 60 is a circuit diagram of an example of an input and output circuit of a semiconductor device according to another embodiment of the invention;

FIG. 61 is a plan view of a typical portion showing a device layout of an input and output circuit cell of a semiconductor device according to another embodiment of the invention; and

FIG. 62 is a plan view of a typical portion showing the peripheral power supply device laid out in FIG. 61.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the description of the embodiments of the invention, the terms “made of copper”, “copper used as a main wiring material” or “a material made mainly of copper” are intended to mean “the use of copper as a main component”, for example. More particularly, it is a matter of course that impurities are usually present in copper of high purity. In this sense, to contain additives or impurities in members made of copper is not excluded herein. Moreover, such expressions as mentioned above include those built-up structures wherein a metal layer made of a material other than copper is formed on a surface of a member made of copper. This is not limited only to copper, but is true of other types of metals, such as, for example, aluminum, titanium nitride and the like. Although, in the description of the invention, the subject matter may be divided into a plurality of sections or embodiments, if expediently necessary, these divisions are not to be considered mutually irrelevant to one another unless otherwise stated. More particularly, one may be in the relation of a modification, details, supplemental explanation and the like of part or all of the others. In the following examples, where reference is made to a number of elements (including the number, numerical value, quantity, range and the like), they should not be construed as limited to specified values or numbers, respectively, except in the case where they are specified or limited to a specific value apparently in principle. That is, those values smaller or larger than the respective specified values may also be within the scope of the invention. Moreover, it is as a matter of course that constituent elements (including steps) in the following embodiments are not always essential, except in the case where otherwise specified or where such elements are considered to be apparently essential in principle. Likewise, if reference is made to the shape, positional relation and the like of constituent elements, then substantially the like or similar shapes and the like are also within the scope of the invention, except in the case where otherwise specified or where such shapes should not be apparently included in principle. This is also true of the above-indicated numbers and ranges. Throughout the drawings, like reference numerals indicate like parts or members having the same function, and a repeated explanation thereof is omitted. In the drawings, plan views may be hatched in some cases for ease in understanding the subject matter. In the embodiments, MIS-FET (metal insulator semiconductor field effect transistor) is referred to simply as MIS, p-channel MIS-FET is referred to as pMIS, and n-channel MIS-FET is referred to as nMIS. The embodiments of the invention will be described in detail with reference to the accompanying drawings.

Embodiment 1

The problem discovered for the first time by us will be described with reference to FIG. 1. FIG. 1 is a sectional view showing a typical portion of a semiconductor device in the course of the manufacture thereof. A semiconductor substrate (hereinafter referred to simply as a substrate) 50S of a wafer 50W is made, for example, of silicon (Si) single crystal and is electrically connected to a ground potential G at the back side thereof. The figure shows a state where a four-layered wiring structure is formed on the main surface (device-forming surface) of the substrate 50S. This four-layered wiring structure has a wiring 51 and an insulating film 52. The wiring 51 is made of a metal which is mainly composed, for example, of aluminium. A wiring portion 51A of the wiring 51 is electrically connected to the substrate 50S. On the other hand, a wiring portion 51B having a great wiring length (e.g. about 500 μm or over) is in a floating (i.e., electrically unconnected or floating wiring) state because of the fact that the semiconductor device is in the course of the manufacturing process. These wirings 51A and 51B are arranged in a proximate condition as a second wiring layer. The insulating film 52 is made, for example, of silicon oxide (SiO₂ or the like) and has the function of insulating the wirings 51. The existing insulating film 52 is provided for complete insulation.

Under these circumstance, if the insulating film 52 is cleaned on the upper surface thereof, for example, with a brush BR, then an electric charge is generated on the upper surface of the insulating film 52 by electrostatic action, thereby causing the wiring 51 to be charged. This charging phenomenon is not limited to the cleaning with the brush BR, but is experienced through other processings as well, including, for example, spin cleaning with pure water, dry etching of wirings per se, plasma treatment for removing a photoresist film by ashing, and the like. If a charge accumulation in the wiring 51 exceeds a given level, a discharge takes place between the wirings 51A and 5B. More particularly, the electric charge accumulated in the floating wiring 51B runs, as shown by the arrows in FIG. 1, into the wiring portion 51A, which is connected to the ground potential G through the insulating film 52 and is lower in potential. At this time, a very high potential difference occurs between the wirings 51A and 51B owing to the charge accumulated in the wiring portion 51B, so that neighboring portions of the wirings 51A, 51B are instantaneously subjected to a high potential difference of several hundreds to several thousands of volts, thereby permitting a high heating temperature as high as one thousand and several hundreds of degrees centigrade to be generated. This causes the wirings 51A, 51B to be deformed at the neighboring portion thereof, with the attendant problem that the wirings 51A, 51B undergo short-circuiting at the neighboring portion. Especially, this problem is liable to be encountered in a case where, because a long wiring is apt to accumulate an electric charge, at least one of the wirings has a great wiring length. The short-circuiting is apt to occur at a neighboring portion of wirings having a high potential difference relative to each other, such as a portion between the wiring 51A connected to the ground potential G and the floating wiring 51B. Moreover, this becomes obvious when the adjacent space of the wirings 51 is rendered narrow as a result of a high degree of integration of the wirings 51 (according to our study, this has been frequently experienced when the space is at a pitch of about 0.8 μm or below). Such a problem as set out hereinabove is one that has been confirmed by us for the first time. At present, the existence of a long wiring and such a wiring connection in the course of the manufacture of a semiconductor device as set forth above (i.e. one of the wirings is connected to a ground potential and the other is in a floating connection condition) have never been taken into account in the art.

To avoid the above-mentioned problem, according to this embodiment, a film through which a minute electric current passes is used as the insulating film between the wirings. In this way, discharge is enabled at a stage where a charge accumulation in the wirings is low. Thus, heat generation can be suppressed to a low level, thereby suppressing or preventing a failure in short-circuiting between the wirings. This can lead to improved yield and reliability of semiconductor devices. The improved yield of semiconductor device results in an expected reduction in the cost of the device. This will be more particularly described below.

FIG. 2 shows an example of a semiconductor device according Embodiment 1, and FIG. 3 shows an enlarge, sectional view of the region A of FIG. 2. A substrate 1S is made, for example, of silicon (Si) single crystal. The substrate 1S has on the main surface thereof (device-forming surface) a groove isolation 2, such as SGI (shallow groove isolation) or STI (shallow trench isolation), formed therein. This isolation 2 is formed, for example, by burying a silicon oxide film in a groove formed in the main surface of the substrate 1S. Moreover, a p-well PWL and an n-well NWL, respectively, are formed at the main surface side of the substrate 1S. For example, boron is introduced into the p well PWL and phosphorus is introduced into the n well NWL. At the active regions of the p well PWL and the n well NWL defined with the isolation 2, devices such as nMISQn and pMISQp are formed. The nMISQn has an n-type semiconductor region 3N for source and drain, a gate insulating film 4 and a gate electrode 5. The pMISQp has a p-type semiconductor region 3P, a gate insulating film 4 and a gate electrode 5. The gate insulating film 4 is made, for example, of a silicon oxide film. The gate electrode 5 is constituted, for example, of a polysilicon film alone, an arrangement of a silicide film, such as cobalt silicide or the like, formed on a polysilicon film, or a built-up arrangement wherein a metal film, such as tungsten or the like, is built up on a polysilicon film through a barrier film, such as of tungsten nitride or the like.

The substrate 1S has, for example, a five-layered wiring structure formed on the main surface thereof. The five-layered wiring structure has a wiring portion 6 and an insulating portion 7. The wiring portion 6 has a wiring 6 a formed between adjacent layers of the respective wiring layers M1 to M5 and a plug 6 b between adjacent wiring layers or between the wiring and the substrate. The wiring 6 a may be formed, for example, of a single conductor film made of aluminium (Al), an aluminium-silicon-copper (Cu) alloy, an aluminium-silicon alloy, a aluminium-copper alloy or the like. In this embodiment, a case where a built-up film made up of conductor films 6 a 1, 6 a 2 and 6 a 3 is illustrated. The lowermost, relatively thin conductor film 6 a 1 is a functional film, which has the function of suppressing or preventing, for example, the constituent atoms of the wiring 6 a and the substrate 1S from being diffused and also the function of improving the adhesion between the wiring 6 a and the insulating portion 7. The film 6 a 1 is constituted, for example, of a single film of titanium nitride (TiN) or a built-up film of titanium formed on titanium nitride. The relatively thick conductor film 6 a 2 formed thereon is formed of a single film of a conductor, which is made of a main wiring material including, for example, aluminium (Al) or an aluminium-silicon-copper (Cu) alloy. The uppermost, relatively thin conductor film 6 a 3 is a functional film, which has, aside from the functions of the above-mentioned conductor film 6 a 1, the function of reducing or preventing halation upon exposure to light for the formation of wiring, and it is formed, for example, of a single film of titanium nitride or a built-up film of titanium nitride built up on titanium. The plug 6 b is a wiring portion for electrical connection between adjacent wirings 6 a of the wiring layers M1 to M5 or between the wiring 6 a of the wiring layer M1 and the substrate 1S, and it is formed by burying a metal film, such as, for example, tungsten, in a groove, such as a contact hole CH or through-hole TH, formed in the insulating portion 7. The plug 6 b may be constituted of a metal film, such as tungsten, and a conductor film, such as titanium nitride, which is formed relatively thinly around the outer periphery (side surface and bottom surface) of the metal film. Although not limitative, the adjacent pitch of the wirings 6 a of the wiring layers M1 to M3 is, for example, at 0.52 μm. The adjacent pitch of the wirings of the wiring layers M4, M5 is, for example, at 1.04 μm.

The insulation portion 7 is fundamentally constituted, for example, of an insulating film (second insulating films) 7 a (7 a 1 to 7 a 6), such as, for example, a silicon oxide film. At the respective insulating portions of the wiring layers M1 to M5, an insulating film (first insulating films) 7 b (7 b 1 to 7 b 5), whose conductivity is higher than that of the insulating film 7 a, is provided for direct contact with the wiring 6 a of the respective wiring layers M1 to M5 and the plug 6 b. In the figure, a structure wherein the insulating film 7 b is so deposited as to cover the surfaces (side and upper surfaces) of the wiring 6 a is shown. Although not shown in the figure, the insulating film 7 b is so provided as to cover and be in contact with a guard ring formed in the vicinity of an outer periphery of a semiconductor chip as extending along the outer periphery. The insulating film 7 b functions to insulate the adjacent wirings 6 during the normal operation of the semiconductor device and has the function of permitting a minute electric current to pass between adjacent wiring portions 6 upon application of an overvoltage, which is higher than a working voltage of the semiconductor device. More particularly, as described hereinafter, the insulating film 7 b has a low electrical conductivity sufficient to insulate the wiring portions 6, like the insulating film 7 a, within a voltage range (i.e. a voltage of about 20 V or below) of the normal operation of the semiconductor device, thus functioning to insulate the wiring portions 6, like the insulating film 7 a. At an overvoltage, which is higher than a working voltage of the semiconductor device, the insulating film 7 b has the function of permitting a minute electric current to pass between adjacent wiring portions 6, thereby rendering the wiring portions 6 conductive. The provision of such an insulating film 7 b allows the electric charge accumulated in the wiring portion in the course of the manufacture of the semiconductor device to escape to the adjacent wiring portion 6 and the substrate 1S through the insulating film 7 b at a stage where the charge accumulation is low. More particularly, the charge can be discharged at a low accumulation at the wiring portion 6, so that the heat release value generated by the discharge between the adjacent wiring portions 6 can be suppressed to a low level. The thickness of the insulating film 7 a is, for example, at about 30 nm. With the structure of FIG. 3, if the insulating film is formed so as to be too thick, adjacent wirings 6 a, 6 a along the horizontal direction, as viewed in FIG. 3, may not be buried with the insulating film 7 a in some cases. If the thickness of the insulating film 7 b is at about 30 nm, then such a burying failure can be avoided. According to an experiment made by us, it has been difficult from the viewpoint of film formation to form the insulating film to a thickness of 30 nm or below. Mention is made, as a material for the insulating film 7 b, of a silicon-rich silicon oxide film or a silicon nitride (SiON) film, for example. The silicon-rich silicon oxide film is one wherein the composition of the silicon oxide film is represented by SixOy, wherein y/x<2. It has been accepted that the conductivity of a silicon-rich silicon oxide film is ten times higher than that of an ordinary silicon oxide film (SiO₂). It is known that when silicon is introduced into an insulating film (silicon oxide film), the conductivity of the insulating film usually increases and the refractive index of the insulating film becomes high. Accordingly, for measurement of the electrical characteristics of insulating films, a measurement of the refractive index of these films for comparison permits the electrical characteristics for different contents of silicon in the insulating films to be measured. More particularly, according to this embodiment, an insulating film having a high refractive index means an insulating film having a high silicon content or an insulating film having a high conductivity.

FIGS. 4 to 7 show the results of measurement of a current I-voltage V characteristic of silicon oxide films. FIG. 4 shows the I–V characteristic of ordinary silicon oxide (SiO₂), and FIGS. 5 to 7, respectively, show an I–V characteristic in the case where the refractive index n and film thickness t of silicon-rich silicon oxide films are changed. The reason why plural curves are depicted in each figure is that plural chips within a wafer subjected to an experiment under the same conditions are measured. FIG. 8 shows, for comparison, the relation between the refractive index and the electric current of about 30 μm thick silicon oxide films derived from the results of FIGS. 4 to 7. Moreover, FIG. 9 shows the relation between the thickness and the electric current of a silicon-rich silicon oxide film having a refractive index of 1.55. According to FIGS. 4 to 9, it will be seen that a silicon-rich silicon oxide film is more likely to pass an electric current than the ordinary silicon oxide film. It will also be seen that a greater thickness t of the silicon-rich silicon oxide film allows an electric current to be run more greatly. In addition, a higher refractive index n, i.e. a higher content of silicon on the silicon oxide film, makes the electric current pass more greatly. According to the studies made by us, where a silicon-rich silicon oxide film having a refractive index of 1.55 or over is used as a material for the insulating film 7 b, good results are obtained in order to avoid the problem concerning the short-circuiting failure between the wirings.

FIG. 10 shows the results of measurement of the I–V characteristic of a silicon oxynitride film (SiON). This film is more likely to allow an electric current to pass therethrough than the ordinary silicon oxide film (FIG. 4) and the silicon-rich silicon oxide films (FIGS. 5 to 7). In this embodiment, it is possible to use such a silicon oxide film (SiON) as a material for the insulating film 7 b. In this case, as shown in FIG. 10, this film is more likely to pass an electric current than the silicon-rich silicon oxide film, and it exhibits a higher conductivity. Thus, better results are obtained in order to avoid the problem concerning the failure of short-circuiting between the wirings.

Next, an example of a method of manufacturing the semiconductor device of Embodiment 1 will be described.

Initially, an example of a cleaning device of the type used in the course of manufacture of the semiconductor device of Embodiment 1 is shown in FIG. 11. A cleaning device 10 is one wherein foreign matter P is removed from a cleaned surface of a wafer 1W obtained after a desired treatment and has a stage 10 a, a nozzle 10 b, a brush BR and a brush holder 10 c. The cleaning treatment is carried out in the following manner, for example. First, the wafer 1W is mounted in a temporarily fixed state so that the surface of the wafer 1W to be cleaned is in face-to-face relation with the brush BR side. Subsequently, while rotating the stage 10 a, a cleaning fluid, such as pure water, is supplied from the nozzle 10 b toward the surface of the wafer 1W to be cleaned. In this condition, the brush BR is rubbed against the surface of the wafer 1W while spinning the brush BR by rotation of the brush holder 10 c, and it is moved from one end to the other of the wafer 1W along the direction of arrow B in FIG. 11, thereby removing the foreign matter P from the surface of the wafer 1W.

Next, an example of a manufacturing process used in the production of the semiconductor device of Embodiment 1 will be described with reference to FIGS. 12 to 16, which show a sectional view of a typical part of the wafer during steps in the manufacture of the semiconductor device, respectively. FIG. 12 is a sectional view of a typical part of the wiring layers M2, M3 in the wafer 1W during the course of manufacture of the semiconductor device. The wiring layer M2 has an insulating film 7 b 2 formed by a CVD (chemical vapor deposition) method to be described hereinafter so as to cover the wiring 6 a therewith. An insulating film 7 a 3 is deposited on the insulating film 7 b 2 by a CVD method described hereinafter. The insulating film 7 a 3 of the wiring layer M2 is flattened on the upper surface thereof by a CMP (chemical mechanical polishing) method, on which conductor films 6 a 1, 6 a 2, 6 a 3 for the wiring formation of the wiring layer M3 are, respectively, deposited by a sputtering method or the like. These conductor films 6 a 1, 6 a 2, 6 a 3 are subjected to patterning by an ordinary photolithographic technique (hereinafter referred to simply as lithography) and also by a dry etching technique (hereinafter referred to simply as dry etching), thereby forming the wiring 6 a at the wiring layer M3, as is particularly shown in FIG. 13.

Thereafter, as shown in FIG. 14, the insulating films 7 b 3, 7 a 4 are deposited on the wiring layer M3 in this order according to a CVD method, and the upper surface of the insulating film 7 a 4 is flattened by a CMP method. Thereafter, the upper surface (surface to be cleaned) of the insulating film 7 a 4 is cleaned by means of the cleaning device 10 (see FIG. 11) using the brush BR, thereby removing foreign matter from the insulating film 7 a 4. At this stage, the charge generated in the upper surface of the insulating film 7 a by the electrostatic action is accumulated in the wiring 6 a of the respective wiring layers M1 to M3, so that an electric current passes from the floating wiring 6 a to the wiring 6 b connected to the substrate 1S. In this embodiment, however, the insulating film 7 b (7 b 1 to 7 b 3) whose conductivity is higher than that of the insulating film 7 a (7 a 1 to 7 a 4) is provided, so that the charge accumulated in the wiring 6 a can escape through the insulating film 7 b (7 b 1 to 7 b 3) to the ground potential G. Thus, the charge can be discharged at a stage where the charge accumulation in the wiring 6 a is low, thereby making it possible to lower the heat release value generated by the discharge. Thus, a short-circuiting failure between the wirings 6 a and 6 a can be suppressed or prevented. This leads to improved yield and reliability of the semiconductor device. The improved yield of semiconductor device in turn leads to an expected cost reduction of the device.

Next, as shown in FIG. 15, a through-hole TH is formed in the insulating films 7 a 4, 7 b 3 by lithography and dry etching, followed by deposition of a film of a high melting point metal, such as, for example, tungsten, on the main surface of the wafer 1W. The high melting point metal film is polished by a chemical mechanical polishing method so that the film is left only within the through-hole TH, thereby forming a plug 6 b in the through-hole TH. Subsequently, the polished surface is cleaned by means of the cleaning device to remove foreign matter therefrom. In this way, a short-circuiting failure between the wirings can be suppressed or prevented by such an action as set forth hereinabove.

As shown in FIG. 16, after forming the wiring 6 a of the wiring layer M4 in the same way as the wiring 6 a of the wiring layer M3, an insulating film 7 b 4 is deposited, by a CVD method to be described hereinafter, over the entire main surface of the wafer 1W so as to cover the wiring 6 a of the wiring layer M4 therewith. Thereafter, the uppermost wiring layer M5 is formed in the same way as stated hereinabove, thereby completing a semiconductor device through an ordinary manufacturing process of the semiconductor device.

Next, an example of a film-forming procedure used in formation of the insulating film 7 b (7 b 1 to 7 b 5) is illustrated. A case where the insulating film 7 b is formed of a silicon-rich silicon oxide film will be described. FIG. 17 shows an example of film-forming sequences of the insulating films 7 a, 7 b in the case where the insulating film 7 b is formed of a silicon-rich silicon oxide film. It will be noted that the figures in the sequences of gases in FIG. 17, respectively, indicate feeds of gases (unit: sccm=cm³/minute), and the figures in the sequences of “upper electrode HF power and lower electrode LF power” indicate high frequency power (unit: W), respectively.

In this embodiment, the insulating film 7 b is formed by a plasma CVD method using, for example, a silane gas. The plasma CVD apparatus being used is, for example, of a parallel plate type. For a treating gas, a mixture of a silane gas, such as, for example, monosilane (SiH₄) or the like, oxygen (O₂) and a diluent gas, such as Ar or the like, is used. Other types of silane gas, such as disilane (Si₂H₆), TEOS (tetraethoxysilane) or the like, may be used in place of monosilane. Likewise, an oxygen-containing gas, such as nitrous oxide (N₂O), ozone (O₃) or the like, may be used instead of oxygen. The time period of t0 to t1 indicates an idling time, the time period of t2 to t5 indicates a film-forming time for the insulating film 7 b, and the time period of t5 to t8 indicates a film-forming time for the insulating time 7 a. Along with the wafer 1W starting to be heated from time t1, argon and oxygen begin to be fed into the treating chamber. From time t2, the feed of monosilane into the chamber is started. In this embodiment, in order to render the insulating film 7 b rich in silicon, the flow rate of monosilane during the course of film formation of the insulating film 7 b is larger than that used for the insulating film 7 a. The flow rate of monosilane for the formation of the insulating film 7 b is, for example, at about 77 sccm (=77 cm³/minute), that of oxygen is, for example, at about 97 sccm, and that of argon is, for example, at about 90 sccm. On the other hand, the flow rate of monosilane for the formation of the insulating film 7 a is, for example, at about 70 sccm, that of oxygen is, for example, at about 90 sccm, and that of argon is, for example, at about 90 sccm. In this way, where the insulating film 7 b is formed of a silicon-rich silicon oxide film, the insulating films 7 a, 7 b can be formed within the treating chamber of the same plasma CVD apparatus. Thus, the time required for film formation can be reduced. In addition, the insulating films 7 a, 7 b can be formed in a continuous, stable state, and occasions of contamination with foreign matter can be reduced in number, thereby improving the reliability of the film formation.

Where the insulating film 7 b is formed of silicon oxynitride (SiOX), a plasma CVD method using, for example, a silane gas is also used. For a treating gas, a mixed gas consisting of a silane gas, such as monosilane (SiH₄) or the like, nitrous oxide (N₂O) and a diluent gas, such as helium (He) or the like, is used. Other types of silane gas, such as disilane (Si₂H₆), TEOS (tetraethoxysilane) or the like, may be used in place of monosilane. Ammonia or ammonia and nitrogen may be further added to the above-mentioned mixed gas. If ammonia or nitrogen is added, oxygen (O₂) or ozone (O₃) may be used in place of nitrous oxide. The flow rate of monosilane for the film formation is, for example, at about 50 sccm, that of nitrous oxide is, for example, at about 66 sccm, and that of helium is, for example, at about 1500 sccm. The temperature of the wafer 1W during the film formation is, for example, at about 350° C., and the pressure within the chamber is, for example, at about 5 Torr. (=666.612 Pa).

Embodiment 2

In Embodiment 2, there is a modification of the wiring structure. FIG. 18 shows a sectional view of an essential part of a semiconductor device representing Embodiment 2 at the same portion as region A of FIG. 3. In Embodiment 2, the insulating film 7 b (7 ba to 7 b 5) of the respective wiring layers M1 to M5 are formed as an underlying layer of the wiring 6 a. More particularly, the wiring 6 a is formed on the insulating film 7 b(7 b 1 to 7 b 5) in the respective wiring layers M1 to M5. In Embodiment 2, the lower surface of the wiring 6 a and the upper side surface of the plug 6 b are in contact with the insulating film 7 b(7 b 1 to 7 b 5), respectively. Accordingly, similar results as described in Embodiment 1 can be obtained in Embodiment 2. With this structure, it is not necessary to take into account the burying properties when an insulating film is buried between adjacent wirings 6 a, 6 a of the same wiring layer, and, thus, the insulating film 7 b can be made thicker than in the case of Embodiment 1. This eventually leads to an increased conductivity of the insulating film 7 b, thereby ensuring improved static elimination.

An example of the manufacturing process used in the formation of a semiconductor device according to Embodiment 2 is illustrated with reference to FIGS. 19 to 23, which are, respectively, sectional views of a wafer during steps in the manufacture of a semiconductor device. FIG. 19 is a sectional view of the wiring layer M1 in the wafer 1W in the course of manufacture of the semiconductor device of FIG. 18. The first-layer wiring 6 a is formed on the insulating film 7 b 1 of the wiring layer M1. This wiring 6 a is covered with the insulating film 7 a 2. Next, the insulating film 7 b 2 is deposited, as shown in FIG. 20, on the insulating film 7 a 2 of the wiring layer M1 in the same manner as in the foregoing Embodiment 1. Subsequently, as shown in FIG. 21, a through-hole TH is formed in the insulating films 7 b 2 and 7 a 2 by lithography and dry etching, followed by formation of the plug 6 b in the through-hole TH in the same manner as in Embodiment 1. Thereafter, as shown in FIG. 22, the wiring 6 a for wiring layer M2 is formed over the insulating film 7 b 2 as similar to the first embodiment; and, thereafter, the insulating later 7 a 3 is deposited so as to cover the wiring 6 a, and, further, the insulating film 7 b 3 is deposited as shown in FIG. 23. With respect to the wiring layers M4, M5, a similar procedure is repeated to complete a semiconductor device using an ordinary process of manufacture of a semiconductor device. In the case of this structure, cleaning is carried out by means of the cleaning device 10 (see FIG. 11) using the brush BR after the step of forming the plug 6 b or after the deposition of the insulating films 7 a, 7 b. As stated hereinbefore, a charge is accumulated in the wiring layer 6 a of the respective wiring layers M1 to M3 by electrostatic action, and it will run from the floating wiring 6 a to the wiring 6 a that is connected to the substrate 1S. In this Embodiment 2, the insulating film 7 b is provided, so that the charge accumulated in the wiring 6 a is able to escape via the insulating film 7 b to the ground potential G. Thus, the charge can be discharged when its accumulation is low, so that the heat release value generated by the discharge can be suppressed to a low level. Thus, short-circuiting failure between the wirings is suppressed or prevented. Accordingly, the yield and reliability of the resulting semiconductor device can be improved. The improved yield of the semiconductor device leads to an expected cost reduction of the semiconductor device.

Embodiment 3

In Embodiments 1 and 2, the case where the insulating film 7 b is provided in all the wiring layers M1 to M5, respectively, has been illustrated, but the invention is not limited to this case, since the insulating film 7 b may be provided only in selected wiring layers. For instance, the wiring short-circuiting failure is liable to occur when a long wiring (of about 500 μm or over) exists. In this sense, the insulating film 7 b may be provided only in the uppermost wiring layer and a wiring layer provided therebeneath (e.g. all or selected layers of the wiring layers M4, M5), where a long wiring exists relatively frequently. Moreover, because the wiring short-circuiting failure is apt to occur at a portion where the space between adjacent wirings is narrow (e.g. at a portion where the adjacent wiring pitch is at 0.8 μm or below), the insulating film 7 b may be provided only in the wiring layers having a portion wherein the space between adjacent wirings is narrow (e.g. all or selected layers of the wiring layers M1, M2 and M3). In addition, the insulating film 7 b may be arranged, for example, only in the odd or even wiring layers. For instance, taking into account both a long wiring and the adjacent wiring space, the insulating film 7 b may be provided only in the wiring layers M2, M4. Where a wiring layer made mainly of aluminium and a wiring layer made mainly a high melting metal exists among the wiring layers, the insulating film 7 b is provided in the aluminum-based wiring layer, but it is not provided in the high melting metal-based wiring layer. In this case, the insulating film 7 b may be provided in all layers of the aluminium-based wiring layer. Alternatively, the insulating film 7 b may be formed at selected wiring layers alone among plural wiring layers made mainly of aluminium.

According to Embodiment 3, the deposition steps used in formation of the insulating film 7 b can be reduced in number, so that the wiring short-circuiting failure is suppressed or prevented from occurring because of the reduced number of processing steps.

Embodiment 4

In Embodiment 4, there is a modification of the wiring structure. FIG. 24 is a plan view of the wiring 6 a of the wiring layers M2, M3, and FIG. 25 is a sectional view, taken along line X1—X1 in FIG. 24. The wiring 6 a of the wiring layer M2 is formed so as to be wider (in a dog-bone shape), at a portion which is connected with the wiring 6 a of the wiring layer M3, than other portions thereof, while taking a discrepancy in alignment of the through-hole TH into account. In a conventional wiring forming technique, an insulating film serving as an etching stopper is provided, in some cases, so as to cover the wiring therewith while taking discrepancy in alignment into consideration. With the dog bone shape, no discrepancy of the alignment takes place, so that it is not necessary to provide any insulating film used for an etching stopper. In this embodiment, the insulating film 7 b which is provided so as to cover the wiring 6 a of the wiring layer M2, as shown in FIG. 25, is provided only for the discharge described hereinbefore.

On the other hand, as shown in the sectional view of FIG. 26, with the width of the wiring 6 a being substantially as narrow as the through-hole TH, when the position of the through-hole TH is formed so as to be shifted relative to the wiring 6 a, it may be, in some case, that the insulating film 7 b exposed from the bottom of the through-hole TH and the underlying insulating film 7 a are etched. To avoid this, an insulating film 7 c for use as an etching stopper is provided so as to be superposed on the insulating film 7 b, as shown in FIG. 27. The insulating film is provided so as to escape the charge accumulated in the wiring 6 a and should preferably be in contact with the wring 6 a. The procedure used in forming the through-hole in this case is illustrated with reference to FIGS. 28 to 30.

First, as shown in FIG. 28, a through-hole TH1 is formed using a photoresist pattern (hereinafter referred to simply as a resist pattern) R1 as an etching mask. At this time, the etching selection ratio of the insulating films 7 a and 7 c is so great that the insulating film 7 a is removed under conditions where the insulating film 7 a is more likely to be etched. Subsequently, as shown in FIG. 29, when the insulating film is exposed, the insulating film 7 c is removed under conditions where the insulating film 7 c is more likely to be etched than the insulating film 7 a, thereby forming a through-hole TH2. Finally, the insulating film 7 b, which is exposed from the bottom of the through-hole TH2, is etched, thereby forming a through-hole TH, wherein part of the wiring 6 a is exposed, as shown in FIG. 30. In this case, the insulating film 7 b may be etched more deeply than the upper surface of the wiring 6 a at a discrepancy portion of alignment between the through-hole TH and the wiring 6 a.

Next, FIG. 31 shows an example of the case where Embodiment 4 is applied to the wiring structure of Embodiment 2. In this case, the insulating film 7 a for use as an etching stopper is deposited so as to cover the wiring 6 a therewith, on which the insulating film 7 a is further deposited. If the alignment discrepancy between the through-hole TH and the wiring 6 a takes place, excess etching does not occur. Next, FIG. 32 shows a modification of the wiring structure of Embodiment 4. In this case, the insulating film 7 c for use as an etching stopper is formed as an underlying layer of the wiring 6 a. More particularly, the insulating film 7 c is formed on the insulating film 7 a, on which the wiring 6 a is formed, on which the insulating film 7 b for discharge is further deposited so as to cover the wiring 6 a therewith. In this connection, when an alignment discrepancy arises between the through-hole TH and the wiring 6 a, the insulating film 7 b at the discrepancy may be etched. Nevertheless, the existence of the underlying insulating film 7 c prevents the underlying insulating film 7 a from being etched.

Embodiment 5

In connection with Embodiment 5, application to an element layer will be described. FIG. 33 is a sectional view of a typical portion in the course of manufacture of a semiconductor device for illustrating the problem checked by us. Reference numeral 52 a indicates an insulating film, reference numeral Q50 indicates a MIS, reference numeral 53 indicates a gate insulating film, and reference numeral 54 indicates a gate electrode. The charge and discharge phenomena of such a wiring arrangement as mentioned above involve, aside from the problem of short-circuiting failure between the wirings, a problem of inducing breakage of the gate insulating film 53 provided beneath the gate electrode 54 connected to a long wiring 51B. To avoid this, it is necessary to design the wiring connected to the gate electrode 54 so as to be short. This undesirably requires a larger number of connection wirings, with the attendant problem that the area of wirings increases, thereby leading to an increasing chip size. It is to be noted that the arrow in FIG. 33 indicates the path escape of an electric charge.

In such a case as set out above, when using the arrangements illustrated for the foregoing Embodiments 1 to 4, discharge is caused to take place between adjacent wirings prior to the breakage of the gate insulating film, so that the breakage of the gate insulating film can be reduced or prevented. In this connection, however, the following arrangement is also possible. More particularly, a structure may be used wherein an electric charge is allowed to escape from the gate electrode to the substrate.

FIG. 34 indicates a specific arrangement for this. A sidewall 11 a is formed on the side surfaces of the gate electrode 5. The side surface of the sidewall 11 a is in direct contact with the gate electrode 5, and the bottom of the sidewall 11 a is also in direct contact with the substrate 1S. The sidewall 11 a is formed of an insulating film similar to the insulating film 7 b. In this way, according to Embodiment 5, the electric charge passing through the wiring to the gate electrode 5 is allowed to escape, as shown by arrow C, from the side surface of the gate electrode 5 through the sidewall 11 a to the substrate 1S. Accordingly, the breakage of the gate insulating film ascribed to the charging phenomenon in the wiring can be suppressed or prevented. As a consequence, the wiring connected to the gate electrode 5 can be elongated, thereby reducing the number of connection wirings with the possibility of reducing the chip size. This sidewall 11 a is formed by forming the gate electrode 5, depositing an insulating film for forming the side wall 11 a on a wafer, and etching back the insulating film using an anisotropic dry etching technique.

FIG. 35 shows a modification of FIG. 34. In this instance, the insulating film 7 d for use as an etching stopper is deposited on the main surface of the substrate 1S so as to cover the gate electrode 5 and the sidewall 11 a. The insulating film 7 d is made, for example, of a silicon nitride film. In doing so, not only will such effects as obtained in FIG. 34 be obtained, but also the problem ascribed to the alignment discrepancy of the contact hole CH can be mitigated or avoided. More particularly, if the position of the contact hole CH is shifted, the gate electrode is prevented from being exposed therefrom. This ensures an improved yield of the semiconductor device.

FIGS. 36 and 37 show another modification of FIG. 34. FIG. 37 shows the case where the contact hole CH and the plug 6 b are, respectively, formed in FIG. 36. In this case, the sidewall 11 b at the side surface of the gate electrode 5 is made, for example of a silicon nitride film or silicon oxide film. The insulating film 7 b for discharge is deposited on the main surface of the substrate 1S so as to cover the gate electrode 5 and the sidewall 11 b therewith. In this case, the charge flowing through the wiring to the gate electrode 5 can escape, as shown by arrow D, from the upper surface of the gate electrode 5 through the insulating film 7 b to the substrate 1S. The formation of the sidewall 11 b with a silicon nitride film can mitigate or avoid the problem caused by the alignment discrepancy at the contact hole CH. In this case, the sidewall is formed by etching back, after which the insulating film 7 b is deposited as stated hereinabove.

FIGS. 38 and 39 show a further modification of FIG. 34. FIG. 39 shows a section transverse to the section of FIG. 38. In this modification, a cap insulating film 12 a, that is made, for example, of a silicon oxide film or silicon nitride film, is formed on the gate electrode 5. The insulating film 7 b for discharge is deposited on the main surface of the substrate 1S so as to cover the sidewall 11 b and the cap insulating film 12 therewith. In this case, the charge passing through the wiring to the gate electrode 5 can escape, as shown by arrow E, from a portion in contact with the insulating film 7 b of the plug 6 b within the contact hole CH to the substrate 1S. If the sidewall 11 b and the cap insulating film 12 a, respectively, are formed of a silicon nitride film, or if the insulating film 7 d for use as an etching stopper is formed as in FIG. 35, the problem ascribed to the alignment discrepancy at the contact hole CH can be mitigated or avoided.

FIG. 40 shows a still further modification of FIG. 34. In this modification, the insulating film 7 b for discharge is formed so as to cover the gate electrode 5 at side and upper surfaces thereof. This insulating film 7 b is in contact with the side and upper surfaces of the gate electrode 5, and it is also in contact with the main surface of the substrate 1S. The gate electrode 5 has the sidewall 11 b formed through the insulating film 7 b at the side surfaces thereof. In this case, the charge passing through the wiring to the gate electrode 5 can escape, as shown by arrow F, from the side and upper surfaces of the gate electrode 5 through the insulating film 7 b to the substrate 1S. If the sidewall 11 b is formed of a silicon nitride film, or if the insulating film 7 d is formed as shown in FIG. 35, then the problem ascribed to the alignment discrepancy of the contact hole CH can be mitigated or avoided. For the formation of such an arrangement as set out above, after formation of the gate electrode 5, the insulating 7 d is deposited on the wafer, followed by further deposition of an insulating film for the formation of the sidewall 11 b and etching back the insulating film for the formation of the sidewall 11 b using a dry etching technique.

It will be noted that, although applications to nMISQn have been illustrated in Embodiment 5, this embodiment may be applied as well to a pMISQp. The arrangement of Embodiment 5 exhibits good effects by itself, and when combined with the foregoing Embodiments 1 to 4, good results are also obtained from the standpoint of mitigating and preventing the short-circuiting failure between wirings and the gate insulation breakage.

Embodiment 6

In Embodiment 6, there is application of the invention to a Damascene wiring structure. FIG. 41 is a sectional view of an essential part of a semiconductor device according to Embodiment 6, and FIG. 42 is an enlarged, sectional view of a region G of FIG. 41.

A wiring portion 6 of a wiring structure in the semiconductor device of Embodiment 6 has a wiring 6 c of an undermost wiring layer M0, a wiring 6 d provided in the respective intermediate wiring layers M1 to M4, a wiring 6 a provided in an uppermost wiring layer M5, and a plug 6 b (6 b 1 to 6 b 4) provided between adjacent wirings or a wiring and a substrate. The wiring layers M0 to M4 are provided as a Damascene wiring structure, respectively, and the uppermost wiring layer M5 is formed as such an ordinary wiring structure as illustrated by the foregoing Embodiments 1 and 2. The wiring 6 c of the undermost wiring layer M0 is formed so as to be buried within a wiring groove (i.e. an opening for wiring) 13, and it has a conductor film 6 c 1 for a main wiring material, such as, for example, tungsten or the like, and a conductor film 6 c 2 for a barrier, such as titanium nitride (TiN) or the like, arranged to side and bottom surfaces of the conductor film for the main wiring material. The wiring 6 d in the intermediate wiring layers M1 to M4 is formed so as to be buried within the wiring groove 13, and it has a conductor film 6 d 1 for a main wiring material, such as of copper (Cu) or the like, and a conductor film 6 d 2 for a barrier that is provided at the side and bottom surfaces of the conductor film for the main wiring material and is made of a single film or builtup film of titanium nitride (TiN), tantalum (Ta) or tantalum nitride (TaN). The plugs 6 b 1, 6 b 4 are, respectively, those illustrated in connection with the foregoing Embodiments 1 to 5. The plug 6 b 2 has a conductor film for main wiring material, such as, for example, copper, and a conductor for a barrier that is formed on the side and bottom surfaces of the conductor film for main wiring material and is made, for example, of a single film or built-up film of titanium nitride, tantalum or tantalum nitride. The plug 6 b 3 is formed integrally with the just above wiring 6 d.

The insulating portion 7 has an insulating film 7 a (7 a 1 to 7 a 12), an insulating film 7 b(7 b 1 to 7 b 10) and insulating films 7 d, 7 e, 7 f 1 and 7 f 2. The insulating films 7 a 1 to 7 a 11 may be made, aside from the materials exemplified in the foregoing Embodiment 1, of a single film consisting of an insulating film of low dielectric constant (low-K insulating film), such as, for example, of SiOF, or a builtup structure wherein a silicon oxide film or the like is deposited on the single film. The low-K insulating film is one which has a dielectric constant that is lower than a silicon oxide film and is constituted by an insulating film of low dielectric constant having a dielectric constant similar to a specific inductive capacity of ε=4.1 to 4.3 of the TEOS oxide film. Using the arrangement having the low-K insulating film, the dielectric constant of the insulating film 7 a can be lower as compared to the case where the insulating film 7 a is formed of a silicon oxide film. For the low-K insulating film, an organic polymer material such as, for example, SILK (made by Dow Chemical Co., with specific inductive capacity=2.7, heat-resistant temperature=490° C. or over, and dielectric breakdown voltage=4.0 to 5.0 MV/Vm) or FLARE (made by Honeywell electric Materials, with specific inductive capacity=2.8 and heat-resistant temperature=400° C. or over) of a polyallyl ether (PAE) material, or an organic silica glass (SiOC) material, such as HSG-R7 (made by Hitachi Chemical Co., Ltd., with specific inductive capacity=2.8 and heat-resistant temperature=650° C.), Black Diamond (made by Applied Materials, Inc., with specific inductive capacity=3.0 to 2.4 and heat resistant temperature=450° C.), p-MTES (made by Hitachi Development Co., Ltd., with specific inductive capacity=3.2) or the like may be used. In this case, the dielectric constant can be lowered in a similar way to that mentioned above.

The insulating film 7 e is a film which functions mainly as an etching stopper and is made, for example, of silicon nitride (Si₃N₄ or the like), silicon carbide (SiC) or silicon carbide nitride (SiCN). The reason why the insulating film 7 e is used in the wiring layer M0 without use of the insulating film 7 b for discharge is that the main wiring material for the wiring 6 c of the wiring layer M0 is mainly made of a high melting point metal, such as tungsten, so that no problem of short-circuiting failure between adjacent wirings ascribed to the discharge arises. From this point of view, although the insulating film 7 b 1 may be formed of the insulating film 7 e, the insulating film 7 b 1 is connected via the plug 6 b 2 to the wiring 6 d made of copper in the wiring layer M1 used as a main wiring material, and, thus, it is formed of the insulating film 7 b for discharge. The insulating film 7 b (7 b 1 to 7 b 10) is so arranged as to be in contact with the wirings 6 d, 6 a and the plugs 6 b 2 to 6 b 4. In this manner, Embodiment 6 ensures similar effects as those achieved in the foregoing Embodiments 1, 2. The insulating films 7 a 12, 7 f 1, 7 f 2 are those films serving as a surface protecting film, wherein the insulating film 7 a 12 is made, for example, of a silicon oxide film or the like, the insulating film 7 f 1 is made, for example, of a silicon nitride film or the like, and the insulating film 7 f 2 is made, for example, a polyimide resin film or the like. The insulating films 7 a 12, 7 f 1, 7 f 2 are, respectively, formed at part thereof with an opening 14 through which part of the fifth-layer wiring 6 a is exposed. The portion (bonding pad hereinafter referred to as pad) of the wiring 6 a exposed from the opening 14 is bonded with a bonding wire BW. In Embodiment 6, the insulating film 7 b may be selectively formed in the wiring layers M1 to M4 using copper as a main wiring material, like Embodiment 3. This ensures similar effects as in the foregoing Embodiment 3.

Next, an example of a method of manufacturing the semiconductor device according to Embodiment 6 will be described. FIG. 43 is a sectional view of a typical part of the wafer 1W in the course of the manufacture of semiconductor device of Embodiment 6. In this figure, a case where the wiring 6 d in the first-layer wiring layer M1 has been formed by a single Damascene method is shown. The insulating film 7 b is made, for example, of silicon oxynitride (SiON) or the like. An insulating film 15 a is made, for example, of a silicon oxynitride deposited on the insulating 7 a 6. In this case, if, after deposition of the insulting film 15 a, the film is subjected to cleaning with a cleaning device 10 (see FIG. 11) using the afore-indicated brush BR, an electric charge is accumulated in the wiring 6 d of the wiring layer M1 by electrostatic action, and the charge escapes from the upper surface side of the wiring 6 d via the insulating films 7 b 2, 7 b 1 to the ground potential GP, thereby permitting the charge to be discharged at a stage where the charge accumulation in the wiring 6 d is low. Thus, the heat release value caused by the discharge can be suppressed to a low level. Accordingly, a short-circuiting failure between the wirings 6 d and 6 d using copper as a main wiring material can be suppressed or prevented.

Subsequently, the insulating film 15 a is subjected to patterning by lithography and dry etching, as shown in FIG. 44, after which an antireflective film 16 a is deposited on the main surface of the wafer 1W, followed by further formation of a resist pattern R2 for forming a through-hole. Thereafter, the antireflective film 16 a and the insulating films 7 a 6, 7 b 4, 7 a 5 are etched by use of the resist pattern R2 as an etching mask, thereby forming a through-hole TH, which is substantially circular in plane view, as shown in FIG. 45. The through-hole TH at this stage is not fully opened, with its bottom being stopped at an intermediate portion of the insulating film 7 a 5 along the thickness direction thereof. Thereafter, the resist pattern R2 and the antireflective film 16 a are removed, as shown in FIG. 46, after which the insulating films 7 a 6, 7 a 5 are selectively etched using the insulating film 15 as a mask in a condition where the insulating films 7 b 4, 7 b 3 function as an etching stopper, thereby forming a wiring groove 13 and the through-hole TH, as shown in FIG. 47. The through-hole TH at this stage is not yet fully opened, with its bottom being stopped at the insulating film 7 b 3. Thereafter, the insulating films 15 a, 7 b 3, 7 b 4 are selectively etched, respectively, thereby fully forming the wiring groove 13 and the through-hole (an opening for wiring) TH. Part of the upper surface of the wiring in the wiring layer M1 is exposed from the bottom of the through-hole TH. Next, a conductor 6 d 2 for a barrier, which is made, for example, of a single film of titanium nitride or tantalum nitride or a builtup film thereof, is deposited by sputtering, as shown in FIG. 49, followed by further formation of a conductor film 6 d 1, which is made, for example, of copper or the like by a plating method or CVD method. Thereafter, the conductor films 6 d 1, 6 d 2 are polished by a CMP method to form a buried structure of the wiring 6 d in the second-layer wiring layer M2, as show in FIG. 50. After the CPM treatment, cleaning is carried out by use of the cleaning device 10 using the brush BR (FIG. 11). If an electric charge is accumulated in the wiring 6 d of the wiring layers M1, M2 by electrostatic action, the charge can escape through the insulating films 7 b 1 to 7 b 4 to the ground potential GP, so that discharge is allowed at a stage where the charge accumulation in the wiring 6 d is low and it is possible to suppress the heat release value caused by the discharge to a low level. Thus, a short-circuiting failure between the wirings 6 d, 6 d of the wiring layers M1, M2 made mainly of copper as a main wiring material can be suppressed or prevented. Thereafter, for the main purpose of suppressing and preventing copper from diffusing, the CMP surface is subjected to plasma treatment in an atmosphere of ammonia or hydrogen gas, after which the insulating film 7 b 5 is deposited on the main surface of the wafer 1W so as to be in contact with the upper surface of the wiring 6 d of the wiring layer M2. Thereafter, the insulating film 7 b 5 is cleaned. In this case, the short-circuiting failure of wirings ascribed to the discharge phenomenon between adjacent wirings can be suppressed or prevented in the same manner as set out hereinbefore.

Embodiment 7

In Embodiment 7, a modification in the case of application of the invention to a Damascene wiring structure is considered. FIG. 51 is a sectional view of an essential part at the same portion as region G of FIG. 41 of a semiconductor device of Embodiment 7.

In Embodiment 7, a plurality of insulating films 7 e (7 e 1 to 7 e 10) are provided in the insulating portion 7 of a wiring structure. The insulating film 7 e in this embodiment has, aside from the function as an etching stopper, as set forth hereinbefore, the function of suppressing or preventing copper diffusion, and it is made, for example, of silicon nitride, silicon carbide, silicon carbide nitride or the like, as mentioned hereinbefore. First, the insulating films 7 e 2, 7 e 4, 7 e 6, 7 e 8, 7 e 10, respectively, are provided in contact with the wirings 6 c, 6 d of the respective wiring layers M0 to M4. This ensures an improved capability of suppressing or preventing diffusion of copper in the wiring 6 d of the respective wiring layers M1 to M4. The insulating films 7 e 2, 7 e 4, 7 e 6, 7 e 8, 7 e 10 are provided thereon in contact with such insulating films 7 b 1, 7 b 3, 7 b 5, 7 b 7, 7 b 9 for discharge, as shown in connection with Embodiment 1, and they are made, for example, of a silicon-rich silicon oxide film or a silicon oxynitride (SiON) film. The insulating films 7 b 1, 7 b 3, 7 b 5, 7 b 7, 7 b 9 are in contact with the plugs 6 b 2, 6 b 3 at the side surfaces thereof. On the other hand, the insulating films 7 e 3, 7 e 5, 7 e 7, 7 e 9 are provided on the insulating films 7 a 3, 7 a 5, 7 a 7, 7 a 9, respectively. Moreover, the insulating films for discharge 7 b 2, 7 b 4, 7 b 6, 7 b 8 are provided on and in contact with the insulating films 7 e 3, 7 e 5, 7 e 7, 7 e 9, and they are formed of a silicon-rich silicon oxide film or a silicon oxynitride (SiON) film, respectively. The insulating films 7 b 2, 7 b 4, 7 b 6, 7 b 8 are in contact with the side surfaces of the wiring 6 d of the respective wiring layers M1 to M4. In Embodiment 7, similar effects as those achieved in the foregoing Embodiments 1, 2 can be obtained by the provision of the insulating film 7 b. Likewise, in Embodiment 7, similar effects as attained in Embodiment 3 can be obtained by selective provision of the insulating film 7 b in the wiring layers M1 to M4 using copper as a main wiring material, like the foregoing Embodiment 3. It will be noted that the element layer and the wiring layer 5, respectively, are the same as those of the foregoing Embodiment 6 and are not repeatedly explained here.

Next, an example of a method of manufacturing the semiconductor device according to Embodiment 7 will be described. FIG. 52 is a sectional view of the wafer 1W obtained after completion of similar steps illustrated with reference to FIGS. 43 to 46 in connection with Embodiment 6. The material selected for an insulating film 15 b is the same as that used, for example, as the insulating film 7 e (7 e 2 to 7 e 5) and includes, for example, silicon nitride, silicon carbide, silicon carbide nitride, or the like. The through-hole TH at this stage passes through the insulating films 7 b 4, 7 e 5 but is not fully opened. The bottom of the through-hole TH is stopped at an intermediate portion of the insulating film 7 a 5 along the thickness direction thereof. Subsequently, the insulating films 7 a 6, 7 a 5 are selectively etched under such conditions that the insulating film 15 b is used as a mask and the insulating films 7 e 4, 7 e 5 function as an etching stopper, thereby forming the wiring groove 13 and the through-hole TH, as shown in FIG. 53. The through-hole TH of this stage is not fully opened as well, with its bottom being stopped at the insulating film 7 e 4. Thereafter, the insulating films 15 b, 7 e 5, 7 e 4 are selectively etched to complete the wiring groove (an opening for wiring) 13 and the through-hole (an opening for wiring) TH. Part of the upper surface of the wiring 6 d of the wiring layer M1 is exposed from the bottom of the through-hole TH. Next, like the foregoing Embodiment 6, the wiring 6 d of a buried structure is formed in the wiring layer M2, as shown in FIG. 55. Then, as main purpose for suppressing and preventing copper from being diffused, after plasma treatment of the CMP surface in an atmosphere of ammonia or hydrogen gas, the insulating film 7 e 6 is deposited on the main surface of the wafer 1W by a CVD method, while being in contact with the upper surface of the wiring layer M2, followed by further deposition of the insulating film 7 b 5 by a CVD method.

In Embodiment 7, if an electric charge is accumulated such as in the wiring 6 d or the like during various processing procedures (including, for example, cleaning, plasma treatment and the like) in the course of the manufacture, the charge can escape from the side surfaces of the plug 6 d or the side surfaces of the plug 6 b connected thereto via the insulating film 7 b to the ground potential, thereby permitting the charge to be discharged at a stage of low accumulation in the wiring 6 d. Thus, the heat release value caused by the discharge can be suppressed to a low level. This results in suppression or prevention of the short-circuiting failure between the wirings 6 d, 6 d, made of copper for a main wiring material, in the wiring layers M1, M2.

Embodiment 8

In Embodiment 8, an example of application of the invention to a measure for static breakage will be considered. FIG. 56 is a plan view of the overall arrangement of a semiconductor chip IV of a semiconductor device of Embodiment 8, FIG. 57 is an enlarged, plan view of region J in FIG. 56, FIG. 58 is a sectional view, taken along line X2—X2 of FIG. 57, and FIG. 59 is a sectional view, taken along line Y1—Y1 of FIG. 57.

At the center of a square planar semiconductor chip 1C, a square planar internal circuit region CA1 is arranged (i.e. a non-hatched region at the center of FIG. 5 and at the left upper portion of FIG. 57). A plurality of processors, such as, for example, a DSP (digital signal processor) and the like, are arranged at the internal circuit region CA1 and the respective processors are so arranged that parallel operations can be performed, while sharing a diversity of processings at the same time. To increase the processing power by carrying out parallel operations of a multitude of instructions and data ensures a real time, high-speed operation of a desired processing, such as image processing. A peripheral circuit region CA2 is arranged from the outer periphery of the internal circuit region CA1 to the outer periphery of the semiconductor chip 1C (i.e. a hatched region of FIGS. 56 and 57).

At the peripheral circuit region CA2, there are arranged a plurality of input and output circuit cells, a plurality of cells (external terminals) PD and a guard ring GR provided therearound. The respective input and output circuit cells have, for example, aside from an input circuit, an output circuit or an input and output bi-directional circuit, various interface circuits, such as a protection circuits for preventing static breakage. The pads PD are arranged at given intervals along the outer periphery of the semiconductor chip 1C. The pads PD include pads for signals and pads for power supply. The pads PD for signals are disposed in every input and output circuit cell. The pads Pd for signals are electrically connected to the semiconductor regions 20 for source and drain of a MISQ ESD forming a protection circuit for preventing static breakage via the plug 6 b and the wiring 6 a of the respective wiring layers M1 to M4. The guard ring GR (GR1 to GR5) not only serves to suppress or prevent impurities and moisture from entering from the outside and also to terminate cracks of insulating films extending from the outer periphery, but also provides a path for permitting an electric charge accumulated in the wiring 6 a in Embodiment 8 to escape to the substrate 1S. The guard ring GR has the same arrangement as the wiring 6 a, and it is formed as a frame in a plane along the outer periphery of the semiconductor chip 1C. In section, the guard rings GR are formed in all the wiring layers M1 to M5, and they are mutually connected with one another through the conductor films 21 within the through-holes TH and also to the substrate 1S via the conductor film 22 within the contact hole CH. Wirings 6 av 1 to 6 av 4, 6 ag 1 t 6 ag 4 (6 a, 6) of the uppermost wiring layer M5 in the peripheral circuit region CA2 indicate wirings for peripheral circuit power supply, respectively. The wirings 6 av 1 to 6 av 3 indicate a wiring for a high potential power supply voltage, for example, of about 3.3 V, and the wiring 6 av 4 indicates a wiring for a high potential power supply voltage, for example, of about 1.2 V. The wirings 6 ag 1 to 6 ag 4 indicate those wirings for a reference potential power supply voltage, for example, of 0 (zero) V. The wirings 6 av 1 to 6 av 4 and 6 ag 1 to 6 ag 4 (6 a, 6) are arranged in the form of a frame to surround the internal circuit region CA1 along the outer periphery of the semiconductor chip 1C.

In Embodiment 8, the insulating film 7 b for discharge is patterned by lithography and dry etching so as to cover the peripheral circuit CA2 alone, as is particularly shown as the hatched portion in FIGS. 56 and 57. The insulating film 7 b is provided only in the uppermost wiring layer M5, and it is deposited in contact with and covers a plurality of wirings 6 a of the peripheral circuit region CA2 of the uppermost wiring layer M5, a plurality of pads PD and the guard ring GR5. The provision of the insulating film 7 b in this way permits a charge (static electricity) passing from outside of the semiconductor chip 1C to a given pad PD to be dispersed via the insulating film 7 b into other pads PD, the guard ring GR5 and the wirings 6 a and to escape to the substrate 1S. In this manner, the static breakage of the elements formed over the substrate 1S can be suppressed or prevented. Moreover, the protection circuits for static breakage can be reduced in number and occupation area. In addition, the protection circuit per se may not be necessary. Currently, because multistage protection circuits for preventing static breakage are provided in every input and output circuit cell or the area of each protection circuit is increased, both to obtain a satisfactory protecting effect, the chip size undesirably increases. According to Embodiment 8, however, the protection circuit area can be reduced or eliminated, thus resulting in a reduction of the chip size. Using the semiconductor device of Embodiment 8, it becomes increasingly possible to facilitate the miniaturization and portability of electronic instruments. The reason why the insulating film 7 b is provided only at the uppermost wiring layer M5 is that the uppermost wiring layer M5 is the nearest portion where a charge passes from outside of the semiconductor chip 1C and is most effective for eliminating the charge. It should be noted that the invention is not limited to this forming position of the insulating film 7 b, but many alterations may be possible. For instance, the insulating film 7 b may be provided, for example, in all the wiring layers M1 to M5, respectively, or it may be provided in more than two selected layers. The insulating film 7 b is provided at the peripheral circuit CA2 alone, for the reason that the elements of the internal circuit region CA1 do not suffer any static influence. In addition, the insulating film 7 b may be patterned so as to cover the pad PD alone or the pad Pd and the guard ring GR alone in contact therewith.

FIG. 60 shows an example of a circuit arrangement of the peripheral circuit region of the semiconductor device of Embodiment 8. The pad PD is electrically connected to the protection circuit ESD for static breakage protection and to an inverter circuit INV for input circuit. The protection circuit ESD is one which protects the internal circuits from suffering from an overvoltage ascribed to static electricity, and diode DESD and MISQ ESD are exemplified as such a protection circuit ESD. The MISQ ESD in the is arranged to function similarly to a diode-connected diode. The inverter circuit INV has a pMISQpi and a nMISQni, with its output being electrically connected to the internal circuit. In Embodiment 8, the insulating film 7 b is arranged as described above, so that when a high voltage (which is higher than the operation voltage of the semiconductor device) is applied between adjacent pads PD owing to the static action, the adjacent pads PD are electrically connected with each other through the insulating film 7 b.

FIG. 61 shows an example of a device layout of the input and output circuit cell I/O, and FIG. 62 is a plan view wherein wirings for a peripheral circuit power supply are added to the arrangement of FIG. 61. Reference numeral NWL in FIGS. 61 and 62 indicates an n-well, and reference numeral PWL indicates a p-well. The n-wells NWL and the p-wells PWL are arranged in the form of a frame along the peripheral circuit power supply wirings. The input and output circuit cell I/O collectively has a series of circuits necessary for an interface for internal circuits and the outside, such as an input and output buffer. The interface between the signal from the outside (e.g. 3.3 V) and an internal signal (e.g. 1.2 V) is performed through the input and output circuit cell I/O. This requires the input and output circuit cell I/O to be located in the vicinity of the pads PD. In addition, it is necessary that at least two power supply voltages be supplied to the input and output circuit cell I/O. At the protection circuit region nearest to the pad PD, the protection circuit ESD is disposed. An output circuit is arranged at a subsequent-stage output buffer circuit region OBA, and an input circuit, such as the above-mentioned inverter circuit INV or the like, is arranged at an input buffer circuit region IBA, both being operated at a power supply voltage of about 3.3 V. A level shifter circuit region LSA provided in a subsequent stage is one wherein a circuit for converting the voltage level of the input and output signal is arranged, and it is operated at power supply voltage of about 1.2 V. And, a pMIS constituting a circuit of each peripheral circuit region is arranged to the n-well NWL, and a nMIS is disposed at the p-well PWL. The power supply voltages applied to the respective circuits of the peripheral circuit region CA2 are supplied from the wirings 6 av 1 to 6 av 4 and 6 ag 1 to 6 ag 4.

Although the invention has been particularly described based on various exemplary embodiments, the invention should not be construed as limited to these embodiments, and many alterations may be possible without departing from the spirit of the invention.

For instance, the method of forming the insulating film 7 b having such a structure as set out in the foregoing Embodiment 2 may be carried out in the following way. For example, a plasma is formed in an atmosphere containing a silane gas, for example, and the insulating film 7 a is exposed to the atmosphere of the plasma on the surface thereof to form a silicon-rich insulating film on the surface layer of the insulating film 7 a. Alternatively, a plasma may be formed in an atmosphere containing nitrogen, followed by exposing the surface of the insulating film 7 a to the plasma atmosphere to form a silicon oxynitride film on the surface layer of the insulating film.

Further, although a connection structure wherein bonding wires are connected to the pads has been illustrated in connection with the foregoing Embodiments 1 to 8, the invention is not limited to this structure, but may be applied to a semiconductor device having connection structure wherein bump electrodes are connected to the pad.

Likewise, although the provision of the insulating film 7 b only at the peripheral circuit region in the foregoing Embodiment 8 has been proposed, the insulating film 7 b may be provided, for example, in the internal circuit region so as to permit an electric charge in the wirings in the course of manufacture to be discharged. In this case, the insulating film 7 b of the peripheral circuit region and the insulating film in the internal circuit region are separated even in the same layer. This not only allows the charge in the wiring during the course of manufacture of a semiconductor device to escape, but it also enables one to disperse a charge generated by the static action at the outside of a semiconductor chip. Because the insulating film 7 b is isolated between the peripheral circuit region and the internal circuit region, an electric charge electrostatically generated at the outside of the semiconductor chip can be prevented from transmitting through the insulating film 7 b.

Although applications to semiconductor devices having a MIS or a logic circuit, which are in the field of utility serving as the background of the invention made by us, have been considered, the invention should not be construed as limited thereto. For instance, the invention is applicable to semiconductor devices having memory circuits, such as, for example, a DRAM (dynamic random access memory), a SRAM (static random access memory), a flash memory (EEPROM: electrically erasable programmable read only memory) and the like, or to consolidated semiconductor devices wherein such a memory circuit as indicated above and a logic circuit are disposed on the same substrate. Alternatively, the invention may be applied to a semiconductor device having a bipolar transistor.

The effects obtained by a typical embodiment according to the invention is briefly described below.

When an insulating film having high conductivity is formed between a wiring that is electrically connected to a semiconductor substrate and a floating wiring, the charge accumulated in the floating wiring in the course of manufacture of a semiconductor device is allowed to be discharged to the electrically connected wiring. Thus, the short-circuiting failure between the wirings can be suppressed or prevented from occurring.

The effects obtained by a typical embodiment according to the invention is briefly described below.

Because an insulating film in a wiring structure of the semiconductor device has a function of permitting an electric charge accumulated in the wiring to escape, the short-circuiting failure ascribed to the discharge of the charge in the wiring can be suppressed or prevented from occurring. 

1. A method of manufacturing a semiconductor device comprising the steps of: (a) forming a first wiring and a second wiring over a semiconductor substrate; (b) after said step (a), forming a first insulating film in contact with said first and second wirings; (c) after said step (b), forming a second insulating film over said first insulating film; (d) after said step (c), cleaning a surface of said second insulating film; (e) after said step (d), forming a plurality of holes in said first and second insulating films; and (f) after said step (e), forming a third wiring over said second insulating film, said third wiring being connected to said first and second wirings via said holes, wherein, in between said step (a) and said step (e), said first wiring is in a floating state and said second wiring is connected to said semiconductor substrate, and wherein said first insulating film is formed so as to have an electric conductivity higher than said second insulating film, so that an electric charge accumulated in said step (d) is escaped through said first insulating film.
 2. The method according to claim 1, wherein said first insulating film is formed in all wiring layers, respectively.
 3. The method according to claim 1, wherein said first wiring is formed only in one or plural wiring layers selected from all wiring layers.
 4. The method according to claim 1, said step (a) comprises a step of depositing a conductor film for the formation of said wiring and thereafter patterning said film by etching.
 5. The method according to claim 4, wherein said wiring is made of aluminium or an aluminium alloy used as a main wiring material.
 6. The method according to claim 1, wherein the step (a) comprises the step of forming an opening for wiring and thereafter burying a conductor film in said opening for wiring thereby forming a wiring.
 7. The method according to claim 6, wherein said wiring is made of copper used as a main wiring material.
 8. The method according to claim 1, wherein said first insulating film and said second insulating film are, respectively, formed by a chemical vapor deposition method, and wherein a flow rate of a silane gas used for the formation of said first insulating film is larger than a flow rate of a silane gas used for the formation of said second insulating film.
 9. The method according to claim 8, wherein the content of silicon in said first insulating film is higher than a content of silicon in said second insulating film.
 10. The method according to claim 9, wherein said first insulating film is made of a silicon-rich silicon oxide film.
 11. The method according to claim 1, wherein said first insulating film comprises, at least, silicon, oxygen and nitrogen.
 12. The method according to claim 11, wherein said first insulating film is made of a silicon oxynitride film.
 13. The method according to claim 1, further comprising a step of forming a MISFET in said semiconductor substrate before said step (a), wherein said first and second wirings are formed over said MISFET, respectively.
 14. The method according to claim 1, wherein said first wiring has a length that is longer than the length of said second wiring.
 15. The method according to claim 14, wherein the length of said first wiring is 500 μm or over.
 16. The method according to claim 1, wherein the pitch between said first wiring and said second wiring is 0.8 μm or below.
 17. A method of manufacturing a semiconductor device comprising the steps of: (a) forming a first wiring and a second wiring over a semiconductor substrate, wherein said first wiring is not connected to said semiconductor substrate and said second wiring is connected to said semiconductor substrate; (b) after said step (a), forming a first insulating film such that said first insulating film covers said first and second wirings; (c) after said step (b), forming a second insulating film over said first insulating film, wherein said first insulating film has an electric conductivity higher than said second insulating film; (d) after said step (c), cleaning a surface of said second insulating film; (e) after said step (d), forming a plurality of holes in said first and second insulating films; and (f) after said step (e), forming a third wiring over said second insulating film, wherein said third wiring is connected to said first and second wirings via said holes.
 18. The method according to claim 17, wherein said first and second insulating films are, respectively, formed by a chemical vapor deposition method, and wherein a flow rate of a silane gas used for the formation of said first insulating film is larger than a flow rate of a silane gas used for the formation of said second insulating film.
 19. The method according to claim 17, wherein the content of silicon in said first insulating film is higher than a content of silicon in said second insulating film.
 20. The method according to claim 17, wherein said first insulating film is made of a silicon-rich silicon oxide film.
 21. The method according to claim 17, wherein said first insulating film comprises a silicon, an oxygen and a nitrogen.
 22. The method according to claim 21, wherein said first insulating film is made of a silicon oxynitride film.
 23. The method according to claim 17, wherein said step (a) comprises: forming a first titanium nitride film over said semiconductor substrate: forming an aluminum film over said first titanium nitride film; forming a second titanium nitride film over said aluminum film; and patterning said first titanium nitride film, said aluminum film and said second titanium nitride film, and wherein in said step (b), said first insulating film covers side surfaces of said first and second wirings.
 24. The method according to claim 17, further comprising a step of polishing said second insulating film between said steps (c) and (d).
 25. The method according to claim 17, wherein in said step (d), a brush is used for said cleaning.
 26. The method according to claim 17, further comprising a step of forming a MISFET in said semiconductor substrate before said step (a), wherein said first and second wirings are formed over said MISFET, respectively.
 27. The method according to claim 17, wherein said first wiring has a length that is longer than the length of said second wiring.
 28. The method according to claim 27, wherein the length of said first wiring is 500 μm or over.
 29. The method according to claim 17, wherein the pitch between said first wiring and said second wiring is 0.8 μm or below. 